Array substrate for IPS-mode LCD device being capable of preventing wavy noise

ABSTRACT

Provided is an array substrate for an IPS-mode LCD device and method of fabricating the same that prevents a problem referred to as wavy noise. The IPS-mode LCD device and method have a shorter processing time and low error rate without an increase in fabrication and production costs.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Divisional of application Ser. No. 11/639,314filed Dec. 15, 2006, now U.S. Pat. No. 7,796,225, which claims priorityto Korean Patent Application No. 10-2005-0133525, filed Dec. 29, 2005,all of which are hereby incorporated by reference for all purposes as iffully set forth herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a liquid crystal display (LCD) device.More particularly, the present invention relates to an array substratefor an in-plane switching mode (IPS-mode) LCD device that prevents wavynoise and a method of fabricating the same.

2. Discussion of the Related Art

A related art liquid crystal display (LCD) device uses opticalanisotropy and polarization properties of liquid crystal molecules. Theliquid crystal molecules have a definite alignment direction as a resultof their thin and long shapes. The alignment direction of the liquidcrystal molecules can be controlled by applying an electric field acrossthe liquid crystal molecules. In other words, as the intensity ordirection of the electric field is changed, the alignment of the liquidcrystal molecules also changes. Since incident light is refracted basedon the orientation of the liquid crystal molecules due to the opticalanisotropy of the liquid crystal molecules, images can be displayed bycontrolling light transmissivity.

Recently, since the LCD device including a thin film transistor (TFT) asa switching element, referred to as an active matrix LCD (AM-LCD)device, has excellent characteristics of high resolution and displayingmoving images, the AM-LCD device has been widely used.

The AM-LCD device includes an array substrate, a color filter substrateand a liquid crystal layer interposed therebetween. The array substratemay include a pixel electrode and the TFT, and the color filtersubstrate may include a color filter layer and a common electrode. TheAM-LCD device is driven by an electric field between the pixel electrodeand the common electrode. However, since the AM-LCD device uses avertical electric field, the AM-LCD device has a bad viewing angle.

An IPS-mode LCD device may be used to resolve the above-mentionedproblem. FIG. 1 is a cross-sectional view of a related art IPS-mode LCDdevice. As shown in FIG. 1, the array substrate and the color filtersubstrate are separated and face each other. The array substrateincludes a first substrate 10, a common electrode 17 and a pixelelectrode 30. Though not shown, the array substrate may include a TFT, agate line and a data line. The color filter substrate includes a secondsubstrate 9, a color filter layer (not shown), and so on. A liquidcrystal layer 11 is interposed between the first substrate 10 and thesecond substrate 9. Since the common electrode 17 and the pixelelectrode 30 are formed on the first substrate 10 on a same level, ahorizontal electric field “L” between the common and pixel electrodes 17and 30 is formed.

FIGS. 2A and 2B are cross-sectional views showing turned on/offconditions of the related art IPS-mode LCD device. As shown in FIG. 2A,when the voltage is applied to the IPS-mode LCD device, liquid crystalmolecules 11 a above the common electrode 17 and the pixel electrode 30are unchanged. But, liquid crystal molecules 11 b between the commonelectrode 17 and the pixel electrode 30 are horizontally arranged due tothe horizontal electric field “L”. Since the liquid crystal moleculesare arranged by a horizontal electric field, the IPS-mode LCD device hasa characteristic of a wide viewing angle. FIG. 2B shows a condition whenthe voltage is not applied to the IPS-mode LCD device. Because aelectric field is not formed between the common and pixel electrodes 17and 30, the arrangement of liquid crystal molecules 11 is not changed.

FIG. 3 is a plan view of an array substrate of the IPS-mode LCD deviceaccording to the related art. As shown in FIG. 3, the array substrateincludes a substrate (not shown), a gate line 43, a data line 60, and acommon line 47. The gate line 43 is formed along a first direction ofthe substrate on the substrate. The data line 60 crosses the gate line43 such that the gate and data lines 43 and 60 define a pixel region “P”on the substrate. The common line 47 is parallel to the gate line 43.The common line 47 also crosses the data line 60.

A TFT “Tr”, a switching element, is formed at a crossing portion of thegate and data lines 43 and 60. The TFT “Tr” includes a gate electrode45, a semiconductor layer 51, and source and drain electrodes 53 and 55.The gate electrode 45 extends from the gate line 43 into the pixelregion “P”. The source electrode 53 extends from the data line 60, andthe source and drain electrodes 53 and 55 are separated from each otheron the semiconductor layer 51. Moreover, a plurality of pixel electrodes70 and a plurality of common electrodes 49 are formed on the substratein the pixel region “P”. The plurality of pixel electrodes 70 extendfrom a pixel connection line 68, which contacts the drain electrode 55through a drain contact hole 66. The plurality of common electrodes 49extend from the common line 47 and are alternately arranged with theplurality of pixel electrodes 70. Ends of each pixel electrode areconnected to each other such that the connected portion is defined as asecond storage electrode 69. The second storage electrode 69 overlapsthe common line 47, and a portion of the common line 47 overlapped withthe second storage electrode 69 is defined as a first storage electrode48. The first electrode 69 and second storage electrode 48 compose astorage capacitor StgC.

FIG. 4 is cross-sectional view of a portion taken along the line IV-IVof FIG. 3. As shown in FIG. 4, the array substrate for the IPS-mode LCDdevice according to the related art includes the substrate 40, the gateelectrode 45, the semiconductor layer 51, the source and drainelectrodes 53 and 55, the plurality of pixel electrodes 70, and theplurality of common electrodes 49. The array substrate is fabricatedthrough the following steps. The gate line 43 (of FIG. 3), the gateelectrode 45, the common line 47 (of FIG. 3) and the plurality of commonelectrodes 49 are formed on the substrate 40 by depositing andpatterning a first metal material through a first mask process. Next, agate insulating layer 50 is formed on the substrate 40 including thegate line 43 (of FIG. 3), the gate electrode 45, the common line 47 (ofFIG. 3) and the plurality of common electrodes 49. Then, thesemiconductor layer 51, which includes an intrinsic amorphous siliconlayer 51 a and an impurity-doped amorphous silicon layer 51 b, is formedon the gate insulating layer 50 by depositing and patterning intrinsicamorphous silicon and impurity-doped amorphous silicon through a secondmask process.

And the data line 60 (of FIG. 3), the source electrode 53 and the drainelectrode 55 are formed on the semiconductor layer 51 and the gateinsulating layer 50 by depositing and patterning a second metal materialthrough a third mask process. As mentioned above, the source electrode53 extends from the data line 60, and the source and drain electrodes 53and 55 are separated from each other.

Next, a passivation layer 63 including a drain contact hole 66 is formedon the source and drain electrodes 53 and 55 and the gate insulatinglayer 50 by depositing and patterning an insulating material through afourth mask process. As mentioned above, the drain contact hole 66exposes the drain electrode 55.

Finally, the pixel connection line 68 and the plurality of pixelelectrodes 70 are formed on the passivation layer 63 by depositing andpatterning a transparent conductive material through a fifth maskprocess. The pixel connection line 68 contacts the drain electrode 55through the drain contact hole 66 such that the plurality of pixelelectrodes 70 are electrically connected to the drain electrode 55. Theplurality of pixel electrodes 70 are alternately arranged with theplurality of common electrodes 49.

As discussed above, the array substrate for the IPS-mode LCD deviceaccording to the related art is fabricated through five mask processes.Accordingly, a processing time, an error rate and production costs areincreased, and a production yield is decreased.

To resolve these problems, a fabricating process using four maskprocesses is suggested. However, since the source and drain electrodesdo not cover both ends of the semiconductor layer, a problem, referredto as wavy noise, is caused. The wavy noise means that when the IPS-modeLCD device is turned on or off, a wave pattern appears on a liquidcrystal panel.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to an array substrate foran IPS-mode LCD device and a method of fabricating the same thatsubstantially obviate one or more of the problems due to limitations anddisadvantages of the related art.

An advantage of the present invention is to provide an array substratefor an IPS-mode LCD device and a method of fabricating the same thathave a short processing time and low error rate without an increase in afabrication process and a production cost.

Another advantage of the present invention is to provide an arraysubstrate for an IPS-mode LCD device and a method of fabricating thesame that prevents a problem referred to as wavy noise.

Additional features and advantages of the invention will be set forth inthe description which follows, and in part will be apparent from thedescription, or may be learned by practice of the invention. These andother advantages of the invention will be realized and attained by thestructure particularly pointed out in the written description and claimshereof as well as the appended drawings.

To achieve these and other advantages and in accordance with the purposeof the present invention, as embodied and broadly described herein, anarray substrate for an IPS-mode LCD device comprises a substrate havinga switching region and a pixel region; a gate line on the substrate; agate electrode formed in the switching region and extending from thegate line; a common line substantially parallel to the gate line andseparated from the gate line; first and second common electrodesextending from the common line into the pixel region and separated fromeach other; a gate insulating layer on the gate line, the common lineand the first and second common electrodes, wherein the gate insulatinglayer has a common line contact hole exposing the common line; a dataline crossing the gate line to define the pixel region on the gateinsulating layer; a semiconductor layer corresponding to the gateelectrode on the gate insulating layer; a source electrode and a drainelectrode separated from each other on the semiconductor layer, whereinthe source electrode extends from the data line; a plurality of pixelelectrodes between the first and second common electrodes, wherein theplurality of pixel electrodes are separated from each other andsubstantially parallel to the first and second common electrodes, andeach of the plurality of pixel electrodes extends from the drainelectrode; and a plurality of third common electrodes formed on the gateinsulating layer, wherein the plurality of third common electrodes areconnected to the common line through the common line contact hole andalternately arranged with the plurality of pixel electrodes, wherein thedata line, the plurality of pixel electrodes and the plurality of thirdcommon electrodes are formed on a same layer and with a same material asone another.

In another aspect of the present invention, a method of fabricating anarray substrate for an IPS-mode LCD device comprises forming a gateline, a gate electrode, a first common line, and first and second commonelectrodes on a substrate having a switching region and a pixel regionusing a first mask process, wherein the gate electrode extends from thegate line and is formed in the switching region, the first common lineis substantially parallel to the gate line, and the first and secondcommon electrodes extend from the first common line into the pixelregion; sequentially forming a gate insulating layer, an intrinsicamorphous silicon layer and an impurity-doped amorphous silicon layer onthe gate line, the gate electrode, and the first and second commonelectrodes; forming a common line contact hole in the gate insulatinglayer, an active layer and an impurity-doped amorphous silicon patternby patterning the gate insulating layer, the intrinsic amorphous siliconlayer and the impurity-doped amorphous silicon layer using a second maskprocess, wherein the common line contact hole exposes the first commonline, the active layer corresponds to the gate electrode on the gateinsulating layer and the impurity-doped amorphous silicon pattern has asame shape as the active layer on the active layer; and forming a dataline, a source electrode, a drain electrode, a plurality of pixelelectrodes and a plurality of third common electrodes on the gateinsulating layer, the active layer and the impurity-doped amorphoussilicon pattern using a third mask process, wherein the data linecrosses the gate line to define the pixel region, the source electrodeextends from the data line and contacts the impurity-doped amorphoussilicon pattern, and the drain electrode is separated from the sourceelectrode and contacts the impurity-doped amorphous silicon pattern,wherein the plurality of pixel electrodes are separated each other andsubstantially parallel to the first and second common electrodes, andeach of the plurality of electrodes extends from the drain electrode,and wherein the plurality of third common electrodes contact the firstcommon line through the common line contact hole and are alternatelyarranged with the plurality of pixel electrodes.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention.

In the drawings:

FIG. 1 is a schematic cross-sectional view of a related art IPS-mode LCDdevice.

FIGS. 2A and 2B are cross-sectional views showing conditions of therelated art IPS-mode LCD device when turned-on and turned-off.

FIG. 3 is a plan view of an array substrate for an IPS-mode LCD deviceaccording to the related art.

FIG. 4 is a cross-sectional view of a portion taken along the line IV-IVof FIG. 3.

FIG. 5 is a plan view showing a pixel region of an array substrate foran IPS-mode LCD device according to the present invention.

FIG. 6 is a cross-sectional view taken along the line VI-VI of FIG. 5.

FIG. 7 is a cross-sectional view taken along the line VII-VII of FIG. 5.

FIG. 8 is a cross-sectional view taken along the line VIII-VIII of FIG.5.

FIG. 9 is a cross-sectional view taken along the line IX-IX of FIG. 5.

FIGS. 10A to 10H are cross-sectional views showing processes offabricating a portion taken along the line VI-VI of FIG. 5.

FIGS. 11A to 11H are cross-sectional views showing processes offabricating a portion taken along the line VII-VII of FIG. 5.

FIGS. 12A to 12H are cross-sectional views showing processes offabricating a portion taken along the line VIII-VIII of FIG. 5.

FIGS. 13A to 13H are cross-sectional views showing processes offabricating a portion taken along the line IX-IX of FIG. 5.

FIG. 14 is a cross sectional-view of a portion taken along the lineXIV-XIV of FIG. 5.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Reference will now be made in detail to embodiments of the presentinvention, examples of which are illustrated in the accompanyingdrawings.

FIG. 5 is a plan view showing a pixel region of an array substrate foran IPS-mode LCD device according to the present invention. As shown inFIG. 5, the array substrate includes a substrate (not shown), a gateline 113, a data line 146, a pixel electrode 160, first and secondcommon lines 118 and 121, first, second and third common electrodes 124,127 and 165 and a TFT “Tr”. The gate line 113 is formed along a firstdirection of the substrate on the substrate. The data line 146 crossesthe gate line 113 such that a pixel region “P” is defined on thesubstrate. The data line 146 has a substantially zigzag shape in anexemplary embodiment, but the data line 146 may have a substantiallylinear shape and so on. A gate pad electrode 129, which connects thegate line 113 and an external gate driving circuit (not shown), isformed at an end of the gate line 113 in a gate pad region “GPA”, and adata pad electrode 130, which connects the data line 146 and an externaldata driving circuit (not shown), is formed at an end of the data line146 in a data pad region “DPA”. The data line 146 is connected to thedata pad electrode 130 through a data link line 123 and a data link linecontact hole 171. It is characteristic that the gate pad electrode 129and the data pad electrode 130 are formed on a same layer as each otherwith a same material as each other.

The first and second common lines 118 and 121 are formed on thesubstrate. The first and second common lines 118 and 121 are separatedfrom each other and substantially parallel to each other. The first andsecond common lines 118 and 121 with the first and second commonelectrodes 124 and 127 surround an edge of the pixel region “P”. One endof the first and second common electrodes 124 and 127 are connected tothe first common line 118, and the other end of the first and secondcommon electrodes 124 and 127 are connected to the second common line121. In other words, the first and second common lines 118 and 121 aredisposed in upper and lower sides of the pixel region “P”, and the firstand second common electrodes 124 and 127 are disposed in right and leftsides of the pixel region “P” substantially parallel to the data line146. In addition, since a common connection line 125 connects the firstand second common lines 118 and 121, two to five common line padelectrodes 131, which is less than a number of the first and secondcommon lines 118 and 121 are formed between the gate pad electrodes 129or of only two portions adjacent to the first and second gate padelectrodes 129 to apply a common voltage to the first and second commonline 118 and 121 formed on an entire substrate.

The TFT “Tr” is formed at a switching region (not shown), that is acrossing portion of the gate and data lines 113 and 146. The TFT “Tr”includes the gate electrode 115, the semiconductor layer 145 the sourceelectrode 150 and the drain electrode 153. In an exemplary embodimentaccording to the present invention, the source electrode 150 has a “U”shape, and the drain electrode 153 is inserted into the mouth of the “U”shape of the source electrode 150 with the drain electrode 153 separatedfrom the drain electrode 150. However, in other embodiments of thepresent invention, the source and drain electrodes 150 and 153 may haveother shapes.

The pixel electrode 160 including a first pixel electrode 160 a and asecond pixel electrode 160 b is electrically connected to the drainelectrode 153. The pixel electrode 160 extends from the drain electrode153 into the pixel region “P” and is substantially parallel to the firstand second common electrodes 124 and 127. The third common electrode 165is formed between the first and second pixel electrodes 160 a and 160 band is connected to the first common line 118 through a common linecontact hole 139. The common line contact hole 139 may have first andsecond common line contact holes 139 a and 139 b. The third commonelectrode 165 is formed on a same layer as the first and second pixelelectrodes 160 a and 160 b with a same material as the first and secondpixel electrodes 160 a and 160 b. A common pad contact hole 136 isformed at one end of the first common line 118. In an exemplaryembodiment of the present invention, the pixel electrode 160 has twopixel electrodes, that is the first and second pixel electrodes 160 aand 160 b. However, in another embodiment, the pixel electrode 160 mayhave multiple pixel electrodes, and then the third common electrode 165also has several third common electrodes. When the third commonelectrode 165 includes the several third common electrodes, the severalthird common electrodes are alternately arranged with the multiple pixelelectrodes. A horizontal electric field is generated between the firstcommon electrode 124 and the first pixel electrode 160 a, between thepixel electrode 160 and the third common electrode 165, and between thesecond pixel electrode 160 b and the second common electrode 127.

A portion connecting the pixel electrode 160 and the drain electrode 153overlaps the second common line 121. The second common line 121overlapped with the portion is defined as a first storage electrode 122,and the portion is defined as a second storage electrode 156. The firststorage electrode 122, the second storage electrode 156 and a gateinsulating layer (not shown) interposed between the first and secondstorage electrodes 122 and 156 compose a storage capacitor (not shown).

FIG. 6 is a cross-sectional view taken along the line VI-VI of FIG. 5,FIG. 7 is a cross-sectional view taken along the line VII-VII of FIG. 5,FIG. 8 is a cross-sectional view taken along the line VIII-VIII of FIG.5, and FIG. 9 is a cross-sectional view taken along the line IX-IX ofFIG. 5. The switching region “TrA”, in which the TFT “Tr” is formed, astorage region “StgA”, in which the storage capacitor “StgC” are definedin the pixel region. And the gate pad region “GPA” (of FIG. 5) and thedata pad region “DPA” are defined at a periphery of the pixel region“P”.

As shown in FIGS. 6 to 9, the gate line 113 is formed on the substrate110. The gate line 113 in the switching region “TrA” functions as thegate electrode 115 in an exemplary embodiment of the present invention,but the gate electrode 115 may be formed to extend from the gate line113 into the pixel region “P”. The first and second common lines 118 and121, which are substantially parallel to each other, are formed on thesubstrate 110 and are substantially parallel to the gate line 113. Thegate pad electrode 129 (of FIG. 5) is formed at the end of the gate line113 in the gate pad region “GPA” (of FIG. 5). The data pad electrode 130is formed in the data pad region “DPA” and has a same shape as the gatepad electrode 129 (of FIG. 5). And a data link line 123 (of FIG. 5)contacts the data pad electrode 130 through a data pad contact hole 137and extends to an end of the data line 146.

In the pixel region “P”, the first and second common electrodes 124 and127 extend from the first and second common lines 118 and 121. One endof the first and second common electrodes 124 and 127 is connected tothe first common line 118, and the other end of the first and secondcommon electrodes 124 and 127 is connected to the second common line121. The first and second common lines 118 and 121, and the first andsecond common electrodes 124 and 127 surround an edge of the pixelregion “P”. In the storage region “StgA”, the second common line 121functions as the first storage electrode 122.

The gate line 113, the first and second common lines 118 and 121, thefirst and second common electrodes 124 and 127, the gate pad electrode129 (of FIG. 5), and the data pad electrode 130 may have adouble-layered structure or a triple-layered structure. Moreparticularly, the gate line 113, the first and second common lines 118and 121, the first and second common electrodes 124 and 127, the gatepad electrode 129 (of FIG. 5), and the data pad electrode 130 include afirst metal layer 113 a, 118 a, 121 a, 124 a, 127 a and 130 a,respectively, and a transparent conductive layer 113 b, 118 b, 121 b,124 b, 127 b and 130 b on the corresponding first metal layer 113 a, 118a, 121 a, 124 a, 127 a and 130 a. The first metal layer 113 a, 118 a,121 a, 124 a, 127 a and 130 a is formed of a first metal that has lowresistance properties, and the transparent conductive layer 113 b, 118b, 121 b, 124 b, 127 b and 130 b is formed of a transparent conductivemetal that has anti-rust properties. The first metal may include, forexample, aluminum, aluminum alloy, copper, chrome and molybdenum. Thetransparent conductive metal may include, for example, indium-tin-oxide(ITO) and indium-zinc-oxide (IZO). Moreover, a second metal layer (notshown) may be formed of a second metal between the first metal layer 113a, 118 a, 121 a, 124 a, 127 a and 130 a and the transparent conductivelayer 113 b, 118 b, 121 b, 124 b, 127 b and 130 b such that the gateline 113, the first and second common lines 118 and 121, the first andsecond common electrodes 124 and 127, the gate pad electrode 129 (ofFIG. 5), and the data pad electrode 130 have the triple-layeredstructure. When the first metal is aluminum or aluminum ally, the secondmetal may be molybdenum.

The gate insulating layer 135 is formed on the gate line 113, the firstand second common lines 118 and 121, and the first and second commonelectrodes 124 and 127. The gate insulating layer 135 includes thecommon line contact hole 139, the data link line contact hole 171 (ofFIG. 5), a gate pad contact hole 138 (of FIG. 5) and a data pad contacthole 137. The common line contact hole 139, which has a first and secondcommon line contact holes 139 a and 139 b, exposes the first common line118, and the data link line contact hole exposes the data link line 123(of FIG. 5). The gate pad contact hole 138 (of FIG. 5) and the data padcontact hole 137 expose the gate pad electrode 129 (of FIG. 5) and thedata pad electrode 130, respectively. In an exemplary embodiment of thepresent invention, the common line contact hole 139 has two common linecontact holes, but the common line contact hole 139 may have one or morethan two common line contact holes. The semiconductor layer 145 includesan active layer 141, a first ohmic contact layer 144 a and a secondohmic contact layer 144 b. The active layer 141 is made of an intrinsicamorphous silicon, and the first and second ohmic contact layers 144 aand 144 b are made of an impurity-doped amorphous silicon. The first andsecond ohmic contact layers 144 a and 144 b are disposed on the activelayer 141 and separated from each other.

On the gate insulating layer 135 and the semiconductor layer 145, thedata line 146, the source electrode 150 and the drain electrode 153 areformed. The data line 146 crosses the gate line 113 such that the pixelregion “P” is defined on the substrate 110. The source electrode 150extends from the data line 146 and is disposed on the first ohmiccontact layer 144 a. The drain electrode 153 is separated from thesource electrode 150 and disposed on the second ohmic contact layer 144b. The drain electrode 153 extends into the storage area “StgA”. Thesource electrode 150 covers one end of the first ohmic contact layer 144a and the active layer 141, and the drain electrode 153 covers an end ofthe second ohmic contact layer 144 b and the other end of the activelayer 141.

Though not shown, the data line 146 is connected to the data padelectrode 130 in the data pad region “DPA” through the data link line123 (of FIG. 5), the data link line contact hole 171 (of FIG. 5) and thedata pad contact hole 137. In FIG. 7, the second storage electrode 156in the storage region “StgA” extends from the drain electrode 153 andoverlaps the first storage electrode 122. The first storage electrode122, the second storage electrode 156 and the gate insulating layer 135compose the storage capacitor “StgC” in the storage region “StgA”.

The pixel electrode 160 including the first and second pixel electrodes160 a and 160 b is formed on the gate insulating layer 135. The pixelelectrode 160 extends from the second storage electrode 156 into thepixel region “P” such that the pixel electrode 160 is electricallyconnected to the drain electrode 153. The first and second pixelelectrodes 160 a and 160 b are separated from each other andsubstantially parallel to the first and second common electrodes 124 and127, respectively. The third common electrode 165 is formed between thefirst and second pixel electrodes 160 a and 160 b and connected to thefirst common line 118 through the first and second contact holes 139 aand 139 b.

Since the above-mentioned array substrate for the IPS-mode LCD device isfabricated through three mask processes, a process time and a productioncost decreases. Moreover, since the source and drain electrodes 150 and153 cover both ends of the semiconductor layer 145, the array substratedoes not have a problem of wavy noise.

FIGS. 10A to 10H are cross-sectional views showing processes offabricating a portion taken along the line VI-VI of FIG. 5, FIGS. 11A to11H are cross-sectional views showing processes of fabricating a portiontaken along the line VII-VII of FIG. 5, FIGS. 12A to 12H arecross-sectional views showing processes of fabricating a portion takenalong the line VIII-VIII of FIG. 5, and FIGS. 13A to 13H arecross-sectional views showing processes of fabricating a portion takenalong the line IX-IX of FIG. 5.

FIGS. 10A, 11A, 12A and 13A describe a first mask process. As shown inFIGS. 10A, 11A, 12A and 13A, the first and second common electrodes 124and 127, the gate line 113, the first and second common lines 118 and121, and the data pad electrode 130 are formed on the substrate 110 bydepositing and patterning the first metal and the transparent conductivemetal through the first mask process. The first and second commonelectrodes 124 and 127, the gate line 113, and the first and secondcommon lines 118 and 121 are formed along a side of the pixel region“P”, and the data pad electrode 130 is formed in the data pad region“DPA”. At the same time, the gate pad electrode 129 (of FIG. 5) isformed in the gate pad region “GPA”, and the data link line 123 (of FIG.5), which is connected to the data pad electrode 130 and the data line146, is formed in the data pad region “DPA”. The first and second commonelectrodes 124 and 127, the gate line 113, the first and second commonlines 118 and 121, the data pad electrode 130, and the gate padelectrode 129 (of FIG. 5) have a double-layered structure. The first andsecond common electrodes 124 and 127 extend from the first and secondcommon lines 118 and 121 into the pixel region “P”, and the first andsecond common electrodes 124 and 127, and the first and second commonlines 118 and 121 surround the pixel region “P”. The gate line 113 isformed along a side of the pixel region “P” and functions as the gateelectrode 115 in the switching region “TrA”. The second common line 121functions as the first storage electrode 122 in the storage region“StgA”. The gate pad electrode 129 (of FIG. 5) is formed at the end ofthe gate line 113 in the gate pad region “GPA” (of FIG. 5), and the datapad electrode 130 is formed in the data pad region “DPA” with connectedto the data line 146 (of FIG. 5).

In particular, the first common electrode 124 has a first metal layer124 a and the transparent conductive layer 124 b, and the second commonelectrode 127 has a first metal layer 127 a and a transparent conductivelayer 127 b. The gate line 113 has the first metal layer 113 a and thetransparent conductive layer 113 b. The first common line 118 has thefirst metal layer 118 a and the transparent conductive layer 118 b, andthe second common line 121 has the first metal layer 121 a and thetransparent conductive layer 121 b. The data pad electrode 130 has thefirst metal layer 130 a and the transparent conductive layer 130 b, andthe gate pad electrode 129 (of FIG. 5) also has the first metal layer(not shown) and the transparent conductive layer (not shown). Asmentioned above, the first metal may include aluminum, aluminum alloy,copper, chrome and molybdenum, and the transparent conductive metal mayinclude indium-tin-oxide (ITO) and indium-zinc-oxide (IZO). The firstmetal has the low resistance, and the transparent conductive metal hasanti-rust properties. The second metal layer (not shown) may be furtherformed between the first metal layer 113 a, 118 a, 121 a, 124 a, 127 aand 130 a and the transparent conductive layer 113 b, 118 b, 121 b, 124b, 127 b and 130 b such that the gate line 113, the first and secondcommon lines 118 and 121, the data pad electrode 130, and the gate padelectrode 129 (of FIG. 5) have the triple-layered structure. The secondmetal layer (not shown) may be made of molybdenum.

As shown in FIGS. 10B, 11B, 12B and 13B, the gate insulating layer 135is formed on the substrate 110 including the gate line 113, the firstand second common lines 118 and 121, the data pad electrode 130, and thegate pad electrode 129 (of FIG. 5) by depositing an inorganic insulatingmaterial. The inorganic insulating material may be silicon oxide (SiO₂)or silicon nitride (SiNx). The intrinsic amorphous silicon layer 140 andthe impurity-doped amorphous silicon layer 143 are formed on the gateinsulating layer 135 by sequentially depositing the intrinsic amorphoussilicon and the impurity-doped amorphous silicon. Then, a photoresist(PR) layer 181 is formed on the impurity-doped amorphous silicon layer143 by depositing photoresist. In this exemplary embodiment, thephotoresist is a positive type that a portion irradiated is removed.However, photoresist of a negative type may be used.

A mask 191 is disposed over the PR layer 181. As illustrated in FIGS.11B and 12B, the mask 191 has a transmissive area “TA”, a blocking area“BA”, and a half-transmissive area “HTA”. The half-transmissive area“HTA” has a transmittance that is smaller than that of the transmissivearea “TA” and greater than that of the blocking area “BA”. Thetransmissive area “TA” may have a transmittance of about 100 percentage,and the blocking area “BA” may have a transmittance of about 0percentage. PR patterns having various heights can be obtained by usingthe above-mentioned mask. The transmissive area “TA” corresponds to asymmetric portion from the center of the first common line 118 shown inFIG. 12B and a center of the data pad electrode 130 in FIG. 13B. Thefirst and second common line contact holes 139 a and 139 b (of FIG. 5)are formed in the symmetric portions, and the data pad contact hole 137(of FIG. 5) is to be formed in the center of the data pad electrode 130.The blocking area “BA” corresponds to the switching area “TrA”, and thehalf-transmissive area “HTA” corresponds to other portions. Thesemiconductor layer 145 is to be formed in a portion corresponding tothe blocking area “BA”. Though not shown, the transmissive area “TA”corresponds to a center of the gate pad electrode, in which the gate padcontact hole is to be formed.

As show in FIGS. 10C, 11C, 12C and 13C, a first PR pattern 181 a and asecond PR pattern 181 b are formed on the impurity-doped amorphoussilicon layer 143 by exposing and developing the PR layer 181 using themask 191. The first PR pattern 181 a corresponding to the blocking area“BA” has a first height, and the second PR pattern 181 b correspondingto the half-transmissive area “HTA” has a second height smaller than thefirst height of the BA. The impurity-doped amorphous silicon layer 143corresponding to the transmissive area “TA” is exposed between thesecond PR patterns 181 b.

Next, as shown in FIGS. 10D, 11D, 12D and 13D, the first and secondcommon line contact hole 139 a and 139 b in the first common line 118,the gate pad contact hole 138 (of FIG. 5) in the gate pad electrode 129(of FIG. 5), and the data pad contact hole 137 in the data pad electrode130 are formed by sequentially removing the impurity-doped amorphoussilicon layer 143 exposed between the second PR patterns 181 b, theintrinsic amorphous silicon layer 140 and the gate insulating layer 135.Though not shown, at the same time, the data link line contact hole 171(of FIG. 5) is formed at an end of the data link line 123 (of FIG. 5).The first and second common line contact holes 139 a and 139 b exposethe first common line 118, respectively, and the gate pad contact hole138 (of FIG. 5) exposes the gate pad electrode 129 (of FIG. 5). The datapad contact hole 137 exposes the data pad electrode 130, and the datalink line contact hole 171 (of FIG. 5) exposes the data link line 123(of FIG. 5).

Since the gate pad electrode 129 (of FIG. 5), the data pad electrode130, the first common line 118, and the data link line 123 (of FIG. 5)have an uppermost layer of the transparent conductive metal, there is noproblem of rust. Moreover, since the first and second common linecontact holes 139 a and 139 b are covered with the liquid crystalmolecules, the problem of rust does not occur.

As shown in FIGS. 10E, 11E, 12E and 13E, the second PR pattern 181 b (ofFIGS. 10D, 11D, 12D and 13D) is removed by ashing the first and secondPR patterns 181 a and 181 b, thereby exposing the impurity-dopedamorphous silicon layer 143 below the second PR pattern 181 b. The firstPR pattern 181 in the switching region “TrA” has a smaller height thanthe first height.

As shown in FIGS. 10F, 11F, 12F and 13F, the impurity-doped amorphoussilicon layer 143 exposed by ashing and the intrinsic amorphous siliconlayer 140 are sequentially removed by dry etching such that the gateinsulating layer 135, which corresponds to the intrinsic amorphoussilicon layer 140 removed by dry etching, is exposed. Accordingly, theimpurity-doped amorphous silicon layer 143 exposed by ashing and theintrinsic amorphous silicon layer 140 remain in the switching region“TrA”, and thereby being the ohmic contact layer 144 and the activelayer 141, respectively. Then, the first PR pattern 181 a is removedfrom the ohmic contact layer 144.

As shown in FIGS. 10G, 11G, 12G and 13G, the data line 146 on the gateinsulating layer 135, the source electrode 150 on the ohmic contactlayer 144 and the drain electrode 153 on the ohmic contact layer 144 areformed by depositing and patterning a metal layer (not shown) through athird mask process. The metal layer (not shown) may be made ofmolybdenum. The data line 146 crosses the gate line 113 such that thepixel region “P” is defined. The data line 146 contacts the data linkline 123 (of FIG. 5) through the link line contact hole 171 (of FIG. 5).The source electrode 150 extends from the data line 146 into theswitching region “TrA”, and the drain electrode 153 is separated fromthe source electrode 150 such that the ohmic contact layer 144 isexposed between the source and drain electrodes 150 and 153. The drainelectrode 153 extends into the storage region “StgA” such that the drainelectrode 153 overlaps the first storage electrode 122, therebyfunctioning as the second storage electrode 156. The first storageelectrode 122, the second storage electrode 156 and the gate insulatinglayer 135 interposed between the first storage electrode 122 and thesecond storage electrode 156 compose the storage capacitor “StgC”.

At the same time, the pixel electrode 160 including the first pixelelectrode 160 a and the second pixel electrode 160 b is formed in thepixel region “P”. The first and second pixel electrodes 160 a and 160 bextend from the second storage electrode 156 such that the first andsecond pixel electrodes 160 a and 160 b electrically contact the drainelectrode 153. The first and second pixel electrodes 160 a and 160 b aresubstantially parallel to the first and second common electrodes 124 and127, respectively. Furthermore, the third common electrode 165 is formedin the pixel region “P”. The third common electrode 165 between thefirst and second pixel electrodes 160 a and 160 b contacts the firstcommon line 118 through the first and second common line contact holes139 a and 139 b and is substantially parallel to the first and secondpixel electrodes 160 a and 160 b.

As shown in FIGS. 10H, 11H, 12H and 13H, the first ohmic contact layer144 a and second ohmic contact layer 144 b are formed by removing theohmic contact layer 144 (of FIG. 11G) exposed between the source anddrain electrodes 150 and 153, and thereby exposing the active layer 141.Then, a silicon oxide layer (not shown) may be formed on the activelayer 141 exposed between the first and second ohmic contact layers 144a and 144 b by plasma process under an ambient of oxygen. The siliconoxide layer (not shown) protects the active layer 141. A step of formingthe silicon oxide layer (not shown) is not essential for the arraysubstrate.

In a method of fabricating the array substrate for the IPS-mode LCDdevice according to the present invention, the pixel electrode 160, thethird common electrode 165 and the data line 146 are formed on a samelayer as each other with a same material as each other. Since the sourceand drain electrodes 150 and 153 covers both ends of the semiconductorlayer 145, respectively, the problem of wavy noise does not occur. Also,the data pad electrode 130 is formed on a same layer as the gate padelectrode 129 with a same material as the gate pad electrode 129. Thefirst and second pixel electrodes 160 a and 160 b, and the first, secondand third common electrodes 124, 127 and 165 have bending shapes,thereby forming multi-domains.

The above-mentioned array substrate does not include a passivationlayer. However, since a first alignment layer (not shown) is formed onthe pixel electrode 160, the data line 146 and the third common line165, a problem that the pixel electrode 160, the data line 146 and thethird common line 165 become rusty does not occur. Also, the firstalignment layer covers the data pad electrode 130, the gate padelectrode 129, the data link line 123.

The array substrate is combined with the color filter substrate (notshown) including the color filter layer (not shown) and a secondalignment layer (not shown). And the liquid crystal layer (not shown) isinterposed between the array substrate and the color filter substrate.

FIG. 14 is a cross sectional-view of a portion taken along the lineXIV-XIV of FIG. 5 and shows the data link line 123 and the data linkline contact hole 171. As shown in FIG. 14, the data link line 123includes the first metal layer 123 a and the transparent conductivelayer 124 b is formed on the substrate 110. The data link line 123contacts the data pad electrode 130 (of FIG. 5) through the data padcontact hole 137 (of FIG. 5). The gate insulating layer 135 is formed onthe data link line 123. The gate insulating layer 135 has the data linkline contact hole 171 exposing the data link line 123. The data line 146is formed on the gate insulating layer 135 and contacts the data linkline 123 through the data link line contact hole 171. In FIG. 14, thedata link line 123 has a double-layered structure. Alternatively, thedata link line may have a triple-layered structure as mentioned above.

It will be apparent to those skilled in the art that variousmodifications and variation can be made in the present invention withoutdeparting from the spirit or scope of the invention. Thus, it isintended that the present invention cover the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

1. An array substrate for an IPS-mode LCD device, comprising: asubstrate having a switching region and a pixel region; a gate line onthe substrate; a gate electrode formed in the switching region andextending from the gate line; first and second common lines in one pixelregion, each of the first and second common lines substantially parallelto the gate line and separated from the gate line; a common connectionline being disposed outside of the pixel region and connecting the firstand second common lines, the common connection line being positioned atthe same layer as the first and second common lines and the gate line;one common line pad electrode for applying a common voltage to the firstand second common lines; first and second common electrodes extendingfrom each of the first and second common lines into the pixel region andseparated from each other; a gate insulating layer on the gate line,each of the first and second common lines and the first and secondcommon electrodes, wherein the gate insulating layer has a common linecontact hole exposing one of the first and second common lines; a dataline crossing the gate line to define the pixel region on the gateinsulating layer; a semiconductor layer corresponding to the gateelectrode on the gate insulating layer; a source electrode and a drainelectrode separated from each other on the semiconductor layer, whereinthe source electrode extends from the data line; a plurality of pixelelectrodes between the first and second common electrodes, wherein theplurality of pixel electrodes are separated from each other andsubstantially parallel to the first and second common electrodes, andeach of the plurality of pixel electrodes extends from the drainelectrode; and a plurality of third common electrodes formed on the gateinsulating layer, wherein the plurality of third common electrodes areconnected to the one of the first and second common lines through thecommon line contact hole and alternately arranged with the plurality ofpixel electrodes, wherein the data line, the plurality of pixelelectrodes and the plurality of third common electrodes are formed on asame layer and with a same material as one another, and the data line,the plurality of pixel electrodes and the plurality of third commonelectrodes are formed of an opaque metallic material.
 2. The arraysubstrate according to claim 1, wherein the first and second commonelectrodes are formed at opposite sides of the pixel region.
 3. Thearray substrate according to claim 1, wherein each of the first andsecond common electrodes are connected to the first and second commonlines and are adjacent to the data line.
 4. The array substrateaccording to claim 1, wherein the common line contact hole exposes thefirst common line.
 5. The array substrate according to claim 1, furthercomprising a storage capacitor including the second common line, astorage electrode extending from the drain electrode such that thestorage electrode overlaps the second common line and the gateinsulating layer interposed between the second common line and thestorage electrode.
 6. The array substrate according to claim 1, whereinthe gate line is on a same layer as the first and second commonelectrodes with a same material as the first and second commonelectrodes.
 7. The array substrate according to claim 1, wherein thegate line, the gate electrode, the first common electrode and the secondcommon electrode have one of a double-layered structure and atriple-layered structure.
 8. The array substrate according to claim 7,wherein an uppermost layer of the gate line, the gate electrode, thefirst common electrode and the second common electrode is a transparentconductive material.
 9. The array substrate according to claim 1,further comprising a gate pad electrode and a data pad electrode,wherein the gate pad electrode is connected to the gate line and anexternal gate driving circuit, and the data pad electrode is connectedto the data line and an external data driving circuit.
 10. The arraysubstrate according to claim 9, wherein the gate pad electrode and thedata pad electrode are on a same layer and a same material as the gateline.
 11. The array substrate according to claim 10, wherein the datapad electrode is connected to the data line through a data link line,wherein the data link line is on a same layer as the gate line and asame material as the gate line.
 12. The array substrate according toclaim 11, wherein the gate insulating layer includes a data link linecontact hole exposing an end of the data link line, wherein the dataline is connected to the data link line through the data link linecontact hole.
 13. The array substrate according to claim 10, wherein thegate insulating layer includes a gate pad contact hole exposing the gatepad electrode and a data pad contact hole exposing the data padelectrode.
 14. The array substrate according to claim 1, wherein thesource electrode and the drain electrode cover ends of the semiconductorlayer.
 15. The array substrate according to claim 1, further comprisinga silicon oxide layer formed on the semiconductor layer between thesource and drain electrodes.
 16. The array substrate according to claim1, wherein the semiconductor layer includes an active layer of intrinsicamorphous silicon and an ohmic contact layer of impurity-doped amorphoussilicon layer on the active layer.